Closing device for closing pressure fluid conveying channels in a housing

ABSTRACT

The present invention relates to a closing device for closing pressure fluid conveying channels in a housing by a closing member press fitted into a channel, the outside periphery of the closing member including at least one indentation into which, by press fitting the closing member into the channel, basic material of the housing is deformed to provide a form lock. The housing is made of a malleable aluminum alloy, and the closing member is made of steel.

TECHNICAL FIELD

The present invention relates to a closing device for closing pressurefluid conveying channels in a housing, the outside periphery of theclosing member including at least one indentation into which, duringpress fitting the closing member into the channel, basic material of thehousing is deformed to provide a form lock.

BACKGROUND OF THE INVENTION

German utility model No. 87 16 060 discloses a closing device forclosing bores or channels in which pressure fluid is conveyed. Theclosing device has a positive connection with the housing by a closingmember pressed into a stepped bore. The basic material of the steppedbore, which provides the form lock, is plastically deformed into anindentation between two piston portions on the closing member whichcorrespond to the two bore portions. The closing member is therebyfastened and sealed in the housing bore.

OBJECT OF THE INVENTION

Therefore, an object of the present invention is to provide a closingdevice of the generic type so that a particularly reliable attachmentand sealing of the closing member in the housing is achieved byincurring low manufacturing costs. Another object is to indicate asuitable method of monitoring the press-in operation of the closingmember into the housing.

SUMMARY OF THE INVENTION

According to the present invention, this object is generally achieved bya housing which is made of a malleable aluminum alloy and a closuremember which is made of steel, wherein with respect to the method ofmonitoring the closing of a pressure fluid connection by such a closingmember, the press-in force applied when the closing member is forcedinto the housing is measured, monitored and evaluated as a function ofthe travel covered by the component that is forced in.

The material composites silicon, iron, copper, manganese, magnesium,chrome, zinc and titanium take great influence on the materialproperties of the housing. A certain quantity of each of these chemicalelements is provided in a mass ratio which determines the deformabilityand machineability of the housing.

To permit ease of machining the steel by turning, milling, drilling andchip detaching operations, to render the steel mechanically resistant,and to provide a durable hydraulic seal-tightness of the steel, achemical compound is proposed which determines the above mentionedmaterial properties in the steel within defined quantity limits.

To satisfy the requirements imposed on the materials of the housing andthe closing member, the steel is specified in terms of its necessaryphysical properties by tension tests. To this end, the appropriatecharacteristic quantities of the materials used are a yield strength ofat least 520N/mm² for the steel and at least 230 to 330N/mm² for thealuminum, a tensile strength of at least 520N/mm² to 650N/mm² for thesteel, and at least 310 to 380N/mm² for the aluminum.

To judge whether the material values of the chosen closing device areappropriate for the desired deformability and machineability, which areattained by rather soft to medium-hard materials, a Brinell test ofhardness is applied.

Preferably the malleable square bar of aluminum alloy which ishot-pressed, thermally treated and straightened. This permits qualitiesof use of the semifinished products which are in conformity with thedemands of manufacture and performance.

In a favorable aspect of the present invention, the material structureof the steel is made up of a ferritic basic material in which perlite islaminated. Mechanical treatment of the steel to achieve the shape of theclosing member is thereby facilitated.

An appropriate method of monitoring the operation of forcing the closingmember into the housing is represented by measuring the press-in forceas a function of the travel covered by the component which is pressfitted. This method permits a simple monitoring and documentation,reduced in terms of cost and time, of manufacture and permits reliablydetermining dimension errors, physical properties and the press-indepth.

Further objectives, features, advantages and possible applications ofthe present invention can be seen from the following description of anembodiment, making reference to the accompanying drawing. All featuresdescribed and/or illustrated per se, or in any suitable combinationdesired, represent the subject matter of the present invention,irrespective of their combination in the claims or their appendency.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a schematic partial view of a closing device according to theinvention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 disclose a closing device including a closing member which has agenerally plug-shaped cross-section. The closing member is attached in astepped bore of the generally block-shaped housing 6 by self-clinchedengagement. The point of self-clinched engagement 2 indicated betweenthe housing bore and the closing member 4 is provided by the material ofhousing 6 which is plastically deformed into an indentation 8 in theclosing member 4. On either side of the indentation 8, the closingmember 4 has piston portions of differently large diameters, which arecorrespondingly adapted to the outside bore portion 1 and the insidebore portion 7. During press fitting the closing member 4 into thestepped bore, the piston portions support the deformation of the housingmaterial into the indentations 8. The indentations 8 are compatible witha cavetto-type recess on the periphery of the closing member 4 whichprovides a metallic seal besides the generation of a retaining force.The indentations 8 in the closing member 4 may be freely chosen to alimited extent in terms of their geometry. According to the presentinvention, the closing member 4 is made of steel, preferably ofcold-drawn free-cutting steel, with the result that the shape cuttingoperation of the closing member 4 is facilitated. The closing member 4can be machined without difficulties by turning, milling and drilling.The chemical composition of the closing member 4 which must bepermanently fluid-tight includes, within defined limits of quantity,portions of carbon, silicon, manganese, phosphorus, sulphur, lead andnitrogen ranging from 0 to 1.25% when named in percents in mass for eachof the elements. Manganese reaches the maximum percentage. All otherelements mentioned range between 0.04 and 0.33% of their mass share inthe chemical composition of the steel. To increase the metal cuttingcapacity and to improve the surface smoothness of the closing member 4,the described steel should be alloyed with tellurium and bismuth, ifnecessary. The share in percent in the chemical composition of the steelshould not exceed 0.02% for tellurium and 0.08% for bismuth. Themechanical physical properties of the steel, as required, are therebyachieved and permit a yield strength and tensile strength of at least520N/mm². The elongation at rupture of the steel in the above mentionedcomposition of the chemical elements reaches numerical values which arein excess of 8%. The Brinell hardness of the cold-drawn semifinishedproduct amounts to at least 160 HB. The indicated strength values of thesteel relate to round bar material for the closing member 4 with adiameter of at least 15 mm. Laminated perlite is included in theferritic basic structure of the steel melt for the closing member 4.Possible inclusions of manganese, sulphides and lead should be minimizedand are permitted only in a very fine distribution. Rows of lead are notpermitted.

The housing 6 made of a malleable aluminum alloy is preferablymanufactured from a square bar material. The square bar material ishot-pressed, thermally treated and straightened for being used forpneumatic and hydraulic blocks and for pump housings. A suitablemachineability by milling and drilling and the condition for plasticdeformation and seal-tightness of the housing necessary for theself-clinched engagement 2 is influenced by the respective percent masscontent of the individual elements silicon, iron, copper, manganese,magnesium, chromium, zinc and titanium in the chemical composition ofthe malleable aluminum alloy, limited to a value of 1.2 percent for thementioned elements. In particular, each of the mass shares of theindividual elements, such as manganese, copper, chromium, zinc andtitanium is considerably below the limit value of 1.2%.

This provides the housing 6 with the necessary mechanical propertieswhich achieve a yield strength between 230 and 330N/mm² and a tensilestrength between 310 and 380N/mm². The breaking tension of the malleablealuminum alloy roughly amounts to 12%. The values for the mechanicalproperties achieved transversely to the pressing direction may range upto 15% below the above mentioned values in the longitudinal direction ofthe square bar. The Brinell hardness of the housing 6 in the core of thesquare bar amounts to at least 90 to 110 HB with a load factor equal toten.

The operation of forcing the closing member 4 into the housing 6 ismonitored by a method which identifies possible dimension errors anddiscrepancies from the predetermined material specifications. This issimply done by monitoring by way of measurements a press-in forceapplied by a force generating means 5 to the closing member 4 independence on the travel covered by the component to be forced in(closing member 4). The pickups of measuring data 3 (force controlmeans, travel control means) required to this end are not included inthe contents of the monitoring method disclosed in the presentinvention. Therefore, functional and structural details of the pickupsfor measuring data 3 are not referred to. The travel and the press-inforce determined by measurements, as a force-travel function, will thenbe continuously monitored with respect to characteristic features, suchas slope and points of discontinuity of a characteristic curve made upof the force-travel function. To monitor the press-in operation,tolerance zones for the force variation or travel variation are fixedwhich permit a qualitative evaluation of the press-in operation in thesimplest case.

Thus, a highly resistant closing device for closing bores and channelsthat convey pressure fluid is achieved by the disclosed featuresrelating to material processing and industrial engineering. The need forseparate sealing and retaining arrangements is thereby obviated. Thepresent invention is preferably used for pneumatic and hydraulicassembly units of automotive vehicle brakes.

We claim:
 1. A Closing device for closing pressure fluid conveyingchannels in a housing by a closing member that is press fitted into achannel, the closing member having an outside periphery including atleast one indentation into which basic material of the housing isdeformed during press fitting the closing member into the channel toprovide a form lock,wherein the channel is configured as a stepped borehaving an outside bore portion of large diameter that is remote from apressure fluid side, the outside bore being followed through a step byan inside bore portion of smaller diameter that is close to the pressurefluid side, wherein the closing member has two piston portions ofdiameters that respectively correspond to the diameters of the insideand outside bore portions, and the indentation provided between thepiston portions is undercut relative to the inside bore portion, and thebasic material is press fitted by plastic deformation into theindentation to provide the form lock, an amount of press-in forceapplied to the closing member being continuously measured by forcecontrol means and adjusted as a function of a measurement of a distancetraveled by the closing member, wherein the principal constituent of thehousing is aluminum and the closing member is made of steel.
 2. AClosing device as claimed in claim 1, wherein the housing comprises amalleable aluminum alloy including at least one of the chemical elementsselected from the group consisting of silicon, iron, copper, manganese,magnesium, chromium, zinc, and titanium.
 3. A Closing device as claimedin claim 1, wherein the steel includes at least one of the chemicalelements selected from the group consisting of carbon, silicon,manganese, phosphorus, sulfur, lead, and nitrogen.
 4. A Closing deviceas claimed in claim 1, wherein the yield strength of the steel in thepressing direction is at least 520N/mm², and the yield strength of thealuminum is between 230 and 330N/mm².
 5. A Closing device as claimed inclaim 1, wherein the tensile strength of the steel in the pressingdirection is at least 520N/mm², and the tensile strength of the aluminumis between 310 to 380N/mm².
 6. A Closing device as claimed in claim 1,wherein the breaking tension of the steel in the pressing direction isat least 8%.
 7. A Closing device as claimed in claim 4, wherein theyield strength, tensile strength, and breaking tension in the aluminumtransversely to the pressing direction are up to 15% below theirrespective values in the longitudinal direction.
 8. A Closing device asclaimed in claim 1, wherein the Brinell hardness of the aluminum isbetween 90 HB and 110 HB, and the Brinell hardness of the steel is atleast 160 HB, the Brinell hardness of the aluminum being determined witha load factor equal to 10 in the structure core.
 9. A Closing device asclaimed in claim 1, wherein the aluminum of the housing is formed of ahot-pressed, thermally treated, and straightened square bar.
 10. AClosing device as claimed in claim 1, wherein the material structurecomprises a ferritic basic material in which perlite is laminated.
 11. AMethod of closing pressure fluid conveying channels in a housing by aclosing member that is to be press fitted into a channel, of the closingmember having an outside periphery including at least one indentationinto which basic material of the housing is deformed during pressfitting the closing member into the channel to provide a formlock,wherein the channel is configured as a stepped bore having anoutside bore portion of large diameter that is remote from a pressurefluid side, the outside bore being followed by an inside bore portion ofsmaller diameter that is close to the pressure fluid side, wherein theclosing member has two piston portions of diameters that respectivelycorrespond to the diameters of the inside and outside bore portions, andthe indentation provided between the piston portions is undercutrelative to the inside bore portion, and the basic material is pressfitted by plastic deformation into the indentation to provide the formlock, the method comprising:continuously measuring an amount of press-inforce applied to the closing member using a force control arrangement;measuring a distance traveled by the closing member; and using the forcecontrol arrangement to adjust the amount of press-in force applied tothe closing member as a function of the measured distance traveled. 12.A Method as claimed in claim 11, further comprising:calculating, basedon the measured applied press-in force and distance, a force-travelfunction having characteristic features; and evaluating the measuredpress-in force and the distance traveled with respect to thecharacteristic features of the force-travel function.
 13. A Method asclaimed in claim 12, further comprising monitoring the press-inoperation of the closing member by comparing the force-travel functionwith travel tolerance zones predetermined by measurements.
 14. A Methodas claimed in claim 11, further comprising monitoring the press-inoperation of the closing member by comparing the force-travel functionwith force tolerance zones predetermined by measurements.
 15. A Methodas claimed in claim 11, further comprising monitoring and evaluating acharacteristic curve variation defined by force-travel functions foreach of a plurality of self-clinched engagements provided on the outsidebore portion with respective time delays by respective indentationsserially disposed along the closing member.